Magnetic tape drives are subject to a phenomenon known as "stiction" which is characterized by a strong adhesion between two highly polished surfaces. In a tape drive, stiction usually occurs between the oxide side of the tape and certain components in the tape transport such as the head or tape cleaner.
The stiction phenomenon is aggravated by high ambient temperature or humidity. With the advent of computer systems that are intended to operate in "ordinary" or non-controlled environments, stiction becomes a major problem. In addition, stiction is somewhat dependent on the type or manufacture of the magnetic tape, even to the extent that certain tapes will operate satisfactorily while others will fail completely under identical conditions.
Stiction causes several different problems in a tape drive and under some circumstances may cause complete failure. For example, if the tape is stopped or moving slowly and it adheres to one or more elements of the tape transport, excessively high tension will be required to free the tape. If the tension required is too great, the tape transport may simply shut down to avoid damaging the tape.
Even if the tape transport does not shut down, the tape is likely to break free suddenly, which creates a large amount of slack. If there is too much slack for the tape transport to buffer, the transport may lose its fix on the tape's position, which would render it unable to correctly read or write.
In a conventional start/stop drive, the tape transport is capable of buffering perhaps several inches of tape by vacuum columns. Start/stop drives are also designed to accelerate the tape rapidly with high tension in order to execute commands more quickly. The result is that if the adhesive force is not overwhelming, a start/stop drive will have sufficient power to jerk the tape free and to buffer the attendant slack. For this reason, the stiction problem may become transparent to the user until a tape is actually damaged.
In contrast, however, a streaming tape drive has neither a vacuum column nor capstan and cannot accelerate the tape nearly as fast as a start/stop drive. A streaming tape drive's speed sensor cannot tolerate the high accelerations used in a start/stop drive without slippage and resulting error. Furthermore, the tape buffering capacity of a streaming tape drive is considerably less than that of a start/stop drive. Thus, the stiction phenomenon is a much more serious problem in a streaming tape drive than a start/stop drive.
One previous "solution" to the stiction problem was for the drive manufacturer to certify only particular types of magnetic tape and to guarantee performance only with such tape. This approach is unsuitable for users who may have their own criteria for tape selection. Similarly, the drive manufacturer may specify excessively stringent environmental conditions (e.g. an air conditioned, low humidity room) for guaranteed performance, which again serves to merely transfer the problem to the user.
Another solution was a moveable magnetic head which would retract when the tape stopped or was moving too slowly. This technique is not viable in a mass data storage device which processes data at high densities and is consequently dependent on precise head alignment at all times. Furthermore, this approach does nothing to prevent stiction with other elements of the tape transport such as the tape cleaner.